The present invention relates to a method and apparatus for alerting the authorities when a person holding a gun enters a “safe zone” such as a school, a place of worship, a government building or an airport, where the only guns that are permitted are those carried by security officers (the local and federal police, private security officers and the like).
Certain areas, such as school zones, children's playgrounds, houses of worship, government buildings and public places such as airports, malls and parks where people congregate, appear to be likely targets for active shooters. Police and private security forces are called upon to guard against acts of violence, but rarely do they know in advance when and if a shooting will occur.
Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. The tags contain electronically-stored information. Passive tags collect energy from a nearby RFID reader's interrogating radio waves. Active tags have a local power source (such as a battery) and may operate hundreds of meters from the RFID reader. Unlike a barcode, the tag need not be within the line of sight of the reader, so it may be embedded in the tracked object.
A complete radio-frequency identification system uses tags, or labels attached to the objects to be identified. Two-way radio transmitter-receivers called interrogators or readers send a signal to the tag and read its response.
RFID tags can be either passive, active or battery-assisted passive. An active tag has an on-board battery and periodically transmits its ID signal. A battery-assisted passive (BAP) has a small battery on board and is activated when in the presence of an RFID reader. A passive tag is cheaper and smaller because it has no battery; instead, the tag uses the radio energy transmitted by the reader. However, to operate a passive tag, it must be illuminated with a power level roughly a thousand times stronger than for signal transmission. That makes a difference in interference and in exposure to radiation.
Tags may either be read-only, having a unique, factory-assigned serial number that is used as a key into a database, or may be read/write, where object-specific data can be written into the tag by the system user. Field programmable tags may be write-once, read-multiple; “blank” tags may be written by a user with an electronic product code.
RFID tags contain at least three parts: an integrated circuit for storing and processing information that modulates and demodulates a radio-frequency (RF) signals; a means of collecting DC power from the incident reader signal, and an antenna for receiving and transmitting the signal. The tag information is stored in a non-volatile memory. The RFID tag includes either fixed or programmable logic for processing the transmission and sensor data, respectively.
An RFID reader transmits an encoded radio signal to interrogate the tag. The RFID tag receives the message and then responds with its identification and other information. This may be limited to a unique tag serial number or it may be product-related information such as a stock number, lot or batch number, production date, or other specific information. Since tags have individual serial numbers, the RFID system design can discriminate among several tags that might be within the range of the RFID reader and read them simultaneously.
A passive tag which operates in the so-called “ISM band” of frequencies (902-928 MHz in North America and 865-868 MHz in Europe) can be made inexpensively (about ten cents per tag) and attached to, or inserted into any item that is to be identified.